Leading shares came close yesterday to repeating the collapse seen on Black Monday in October 1987. Indeed, the FTSE 100 suffered its biggest one-day points fall, with investors unnerved by the rapid escalation of the global financial crisis and the growing fears that the world's economies are set to plunge into a serious downturn.

Miners and banks were among the major losers, helping push the index down 391.1 points to 4589.2, its lowest level since October 26, 2004. The 7.85% drop - the third-largest percentage fall on record - meant some £93bn was wiped off the value of Britain's top companies. There was not a single riser on the FTSE 100. The FTSE 250 mid-cap index also saw a dramatic decline, down 520.8 points to 7474.8. On Wall Street, the Dow Jones industrial average lost more than 500 points in early trading and dropped below the 10,000 level for the first time in four years.

Hopes that Alistair Darling would use his statement to announce plans to take stakes in troubled banks and a blanket guarantee for savers proved misplaced. The chancellor's repetition of the mantra that the government would do all that was necessary did little to reassure investors. Royal Bank of Scotland slumped 38.1p to 148.1p - a 20.5% decline - while HBOS fell 39.7p to 160.8p; its suitor, Lloyds TSB, lost 31.25p to 259p, and Barclays dropped 54p to 314p. In a negative note on the sector, analysts at Credit Suisse said: "Trading at around 1.2 times tangible book value, we think the downturn that is coming is absolutely not factored into current [bank] share prices."

Miners fell sharply as metal prices headed south again on concerns about slowing demand, especially from China. Copper lost 8% to reach its lowest level in almost 20 months, while aluminium and nickel also lost ground. Kazakhmys closed down 151.25p to 417.75p, and Eurasian Natural Resources Corp dropped 130p to 555p. Iron-ore specialist Ferrexpo fell 2.5p to 115p after its majority shareholder, Fevamotinico, a company controlled by the Ukrainian billionaire Kostyantin Zhevago, sold a 20.8% stake to the owner of the Czech coal miner New World Resource. The deal, well below the market price at 86p a share, was to satisfy a loan agreement Fevamotinico had with JP Morgan.

With oil also down about $4 to $86 a barrel, Cairn Energy lost 315p to £15.39, while BP dropped 38p to 429.75p. Housebuilders were unwanted, in particular Taylor Wimpey, 7p down at 27.75p, in the wake of Friday's news of a delay in agreeing a relaxation of its banking covenants. On a brighter note, CustomVis, which specialises in solid-state laser systems for eye surgery, jumped 50% to 0.75p after it announced the first sale of its key product in Peru.

'We expect a comparatively reasonable trading statement from Marston's, but to be reassured by this would be wrong. We think the worst is yet to come'.